We analyse Spitzer MIPS 24micron observations, and SDSS (DR7) optical broadband photometry and spectra, to investigate the star formation (SF) properties of galaxies residing in the Coma supercluster region. We find that SF in dwarf galaxies is quenched only in the high density environment at the centre of clusters and groups, but passively-evolving massive galaxies are found in all environments, indicating that massive galaxies can become passive via internal processes. We find AGN activity is suppressed in the cluster cores. We present evidence for a strong dependence of the mechanism(s) responsible for quenching SF in dwarf galaxies on the cluster potential. We find a significant increase in the mean EW of Halpha among star-forming dwarf galaxies in the infall regions of the Coma cluster and the core of Abell 1367 with respect to the overall supercluster population, indicative of the infalling dwarf galaxies undergoing a starburst phase. We identify these starburst galaxies as the precursors of the post-starburst k+A galaxies. We find that 11.4% of all dwarf (z mag > 15) galaxies in the Coma cluster and 4.8% in the Abell 1367 have k+A like spectra, while this fraction is just 2.1% when averaged over the entire supercluster region. We show that in the centre of the Coma cluster, the (24-z) colour of galaxies is correlated with their optical (g-r) colour and Halpha emission. By analysing the projected phase space distribution of galaxies detected at 24micron in Coma, we find that the (optically) red 24 micron detected galaxies follow the general distribution of `all' the spectroscopic members, but their (optically) blue counterparts show interesting features, indicative of recent infall.
We employ spectroscopic and photometric data from SDSS DR7, in a 500 sq degree region, to understand the evolution of dwarf (~M*+2<M_z<M*+4) galaxies in the Coma supercluster (z=0.023). We show that in the Coma supercluster, the red dwarfs are mostly concentrated in the dense cores of the Coma and Abell 1367 clusters, and in the galaxy groups embedded in the filament connecting them. The post-starburst (k+A) dwarfs however are found in the infall regions of the Coma and Abell 1367 clusters, and occasionally in galaxy groups embedded along the filament, suggesting that strong velocity fields pr…
We take a close look at the galaxies in the Coma Supercluster and assess the role of the environment (in the form of cluster, group and supercluster filament) in their evolution, in particular examining the role of groups. We characterise the groups according to intrinsic properties such as richness and halo mass, as well as their position in the supercluster and proximity to the two rich clusters, Abell 1656 (Coma) and Abell 1367. We devise a new way of characterising the local environment using a kernel density estimator. We find that apart from the dominant effects of the galaxy mass, the e…
Superclusters of galaxies can be defined kinematically from local evaluations of the velocity shear tensor. The location where the smallest eigenvalue of the shear is positive and maximal defines the center of a basin of attraction. Velocity and density fields are reconstructed with Wiener Filter techniques. Local velocities due to the density field in a restricted region can be separated from external tidal flows, permitting the identification of boundaries separating inward flows toward a basin of attraction and outward flows. This methodology was used to define the Laniakea Supercluster tha…
We present the analysis of the galaxy structural parameters from Halpha3, an Halpha narrow-band imaging follow-up survey of ~800 galaxies selected from the HI ALFALFA Survey in the Local and Coma Superclusters. Taking advantage of Halpha3 which provides the complete census of the recent star-forming, HI-rich galaxies in the local universe, we aim to investigate the structural parameters of both the young (<10 Myr) and the old (>1 Gyr) stellar populations. By comparing the sizes of these stellar components we investigated the spatial scale on which galaxies are growing at the present cosmologic…
To investigate the dependence of the occurrence of active galactic nuclei (AGNs) on local galaxy density, we study the nuclear properties of ~5000 galaxies in the Coma Supercluster whose density spans 2 orders of magnitude from the sparse filaments to the cores of the rich clusters. We obtained optical spectra of the nuclei of 177 galaxies using the 1.5m Cassini telescope, which are added to the 4785 spectra available from SDSS (DR7) to fill-in the incomplete coverage by SDSS of luminous galaxies. We perform a spectral classification of the nuclei of galaxies (with a completeness of 98% at r<1…
The Cl1604 supercluster at $z \sim 0.9$ is one of the most extensively studied high redshift large scale structures, with more than 500 spectroscopically confirmed members. It consists of 8 clusters and groups, with members numbering from a dozen to nearly a hundred, providing a broad range of environments for investigating the large scale environmental effects on galaxy evolution. Here we examine the properties of 48 post-starburst galaxies in Cl1604, comparing them to other galaxy populations in the same supercluster. Incorporating photometry from ground-based optical and near-infrared imagi…
It is important to map the large-scale matter distribution in the local Universe for cosmological studies, such as the tracing of the large-scale peculiar velocity flow, the characterisation of the environment for different astronomical objects, and for precision measurements of cosmological parameters. We used X-ray luminous clusters to map this matter distribution and find that about 51% of the groups and clusters are members of superclusters which occupy only a few percent of the volume. In this paper we provide a detailed description of these large-scale structures. With a friends-to-frien…
We present the refurbished GOLDMine galaxy site (http://goldmine.mib.infn.it) superseding the one operating since 2002 (Gavazzi et al. 2003). Data for 9704 galaxies selected with r<17.7 mag from the SDSS, belonging to the Cancer cluster, Local supercluster, Coma supercluster, Hercules, A2197 and A2199 clusters are included.
We examine the effects of pre-processing across the Coma Supercluster, including 3505 galaxies over 500 sq deg, by quantifying the degree to which star-forming (SF) activity is quenched as a function of environment. We characterise environment using the complementary techniques of Voronoi Tessellation, to measure the density field, and the Minimal Spanning Tree, to define continuous structures, and so we measure SF activity as a function of local density and the type of environment (cluster, group, filament, and void), and quantify the degree to which environment contributes to quenching of SF…
We explore the variation in stellar population ages for Coma cluster galaxies as a function of projected cluster-centric distance, using a sample of 362 red-sequence galaxies with high signal-to-noise spectroscopy. The sample spans a wide range in luminosity (0.02-4 L*) and extends from the cluster core to near the virial radius. We find a clear distinction in the observed trends of the giant and dwarf galaxies. The ages of red-sequence giants are primarily determined by galaxy mass, with only weak modulation by environment, in the sense that galaxies at larger cluster-centric distance are sli…
We present panoramic Spitzer/MIPS mid- and far-infrared and GALEX ultraviolet imaging of the the most massive and dynamically active system in the local Universe, the Shapley supercluster at z=0.048, covering the 5 clusters which make up the supercluster core. We combine these data with existing spectroscopic data from 814 confirmed supercluster members to produce the first study of a local rich cluster including both ultraviolet and infrared luminosity functions (LFs). This joint analysis allows us to produce a complete census of star-formation (both obscured and unobscured), extending down t…
We present deep GMOS long-slit spectroscopy of 15 Coma cluster S0 galaxies, and extract kinematic properties along the major axis to several times the disc scale-length. Supplementing our dataset with previously published data, we create a combined sample of 29 Coma S0s, as well as a comparison sample of 38 Coma spirals. Using photometry from SDSS and 2MASS, we construct the Tully-Fisher relation (TFR; luminosity versus maximum rotational velocity) for S0 galaxies. At fixed rotational velocity, the Coma S0 galaxies are on average fainter than Coma spirals by 1.10$\pm$0.18, 0.86$\pm$0.19 and 0.…
We investigate the distribution and velocity field of galaxies situated in a band of 100 by 20 degrees centered on M87 and oriented along the Local supercluster plane. Our sample amounts 2158 galaxies with radial velocities less than 2000 km/s. Of them, 1119 galaxies (52%) have distance and peculiar velocity estimates. About 3/4 of early-type galaxies are concentrated within the Virgo cluster core, most of the late-type galaxies in the band locate outside the virial radius. Distribution of gas-rich dwarfs with $M_{\rm H\,I} > M_*$ looks to be insensitive to the Virgo cluster presence. Among 50…
We present an analysis of the mid-infrared (MIR) colours of 165 70um-detected galaxies in the Shapley supercluster core (SSC) at z=0.048 using panoramic Spitzer/MIPS 24 and 70um imaging. While the bulk of galaxies show f70/f24 colours typical of local star-forming galaxies, we identify a significant sub-population of 23 70micron-excess galaxies, whose MIR colours (f70/f24>25) are much redder and cannot be reproduced by any of the standard model infrared SEDs. These galaxies are found to be strongly concentrated towards the cores of the five clusters that make up the SSC, and also appear rare a…
Using deep two-color near-infrared HST imaging and unbiased grism spectroscopy we present a detailed study of the z=1.803 JKCS041 cluster. Uniquely, for a high redshift cluster, we confirm a mass of $\log M=14.2$ in solar units using four different techniques based on the X-ray temperature, the X-ray luminosity and the cluster richness. JKCS041 is thus a progenitor of a local system like the Coma cluster. Our rich dataset and the abundant population of 14 spectroscopically-confirmed red sequence galaxies allows us to explore the past star formation history of this system in unprecedented detai…
We present the analysis of Halpha3, an Halpha imaging survey of galaxies selected from the HI ALFALFA Survey in the Coma Supercluster. By using the Halpha line as a tracer of the "instantaneous" star formation, complemented with optical colors from SDSS we explore the hypothesis that a morphological sequence of galaxies of progressively earlier type, lower gas-content exists in the neighborhood of the Coma cluster, with specific star formation activity decreasing with increasing local galaxy density and velocity dispersion. In the dwarf regime (8.5<\log(M*)< 9.5) we identify a 4-step sequence …
We present the analysis of Halpha3, an Halpha imaging survey of 409 galaxies selected from the HI Arecibo ALFALFA Survey in the Local Supercluster, including the Virgo cluster. We explore the relations between the stellar mass, the HI mass and the current, massive SFR of nearby galaxies in the Virgo cluster and we compare them with those of isolated galaxies in the Local Supercluster, disentangling the role of the environment in shaping the star formation properties of galaxies at the present cosmological epoch. We investigate the relationships between atomic neutral gas and newly formed stars…
The IMACS Cluster Building Survey (ICBS) provides spectra of ~2200 galaxies 0.31<z<0.54 in 5 rich clusters (R <= 5 Mpc) and the field. Infalling, dynamically cold groups with tens of members account for approximately half of the supercluster population, contributing to a growth in cluster mass of ~100% by today. The ICBS spectra distinguish non-starforming (PAS) and poststarburst (PSB) from starforming galaxies -- continuously starforming (CSF) or starbursts, (SBH or SBO), identified by anomalously strong H-delta absorption or [O II] emission. For the infalling cluster groups and similar field…
We present new constraints on the star formation histories of six ultra-faint dwarf galaxies: Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I. Our analysis employs a combination of high-precision photometry obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, medium-resolution spectroscopy obtained with the DEep Imaging Multi-Object Spectrograph on the W.M. Keck Observatory, and updated Victoria-Regina isochrones tailored to the abundance patterns appropriate for these galaxies. The data for five of these Milky Way satellites are best fit…
We present a large-scale galaxy structure Cl J021734-0513 at z~0.65 discovered in the UKIDSS UDS field, made of ~20 galaxy groups and clusters, spreading over 10 Mpc. We report on a VLT/VIMOS spectroscopic follow-up program that, combined with past spectroscopy, allowed us to confirm four galaxy clusters (M200 ~ 10^14 Msol) and a dozen associated groups and star-forming galaxy overdensities. Two additional filamentary structures at z ~ 0.62 and z ~ 0.69 and foreground and background clusters at 0.6 < z < 0.7 were also confirmed along the line-of-sight. The structure subcomponents are at differ…
Stellar population parameters derived from spectral line-strengths provide a powerful probe of galaxy properties and formation histories. We implement the machinery for extracting single-stellar-population-equivalent stellar population parameters from synthetic spectra generated by a hierarchical galaxy formation model. We find that the SSP-equivalent age is related to the light-weighted age in a complicated fashion that reflects the influence of recently-formed stars and is poorly correlated with the mass-weighted age. The tendency for SSP-equivalent ages to be biased young means that archaeo…
We generate probabilistic predictions of the low-redshift ($z < 0.2$) synchrotron Cosmic Web for half of the Northern Sky. In particular, we predict the contribution to the specific intensity function at $ν_\mathrm{obs} = 150\ \mathrm{MHz}$ from merger shocks in clusters and accretion shocks in filaments, both of which arise during large-scale structure formation. We assume a primordial magnetogenesis scenario, but our method is general enough to allow for an exploration of alternative magnetogenesis scenarios - and even alternative radiation mechanisms and spectral windows. In the future, by …
We have studied a sample of 89 very isolated, elliptical galaxies at z < 0.08 and compared their properties with elliptical galaxies located in a high-density environment such as the Coma supercluster. Our aim is to probe the role of environment on the morphological transformation and quenching of elliptical galaxies as a function of mass. In addition, we elucidate the nature of a particular set of blue and star-forming isolated ellipticals identified here. We study physical properties of ellipticals such as color, specific star formation rate, galaxy size, and stellar age, as a function of st…
The Bullet Cluster is a massive galaxy cluster at z=0.297 undergoing a major supersonic (Mach 3) merger event. Using Spitzer 24um images, IRAC data, optical imaging, and optical spectroscopy, we present the global star formation rate (SFR) of this unique cluster. Using a 90% spectroscopically complete sample of 37 non-AGN MIPS confirmed cluster members out to R<1.7 Mpc, and the Rieke et al. (2009) relation to convert from 24um flux to SFR, we calculate an integrated obscured SFR of 267 Msolar/yr and a specific star formation rate of 28 Msolar/yr per 10^14 Msolar. The cluster mass normalized in…
With the aim of quantifying the contribution of the environment on the evolution of galaxies at z=0 we have used the DR7 catalogue of the Sloan Digital Sky Survey (SDSS) to reconstruct the 3-D distribution of 4132 galaxies in 420 square degrees of the Coma supercluster, containing two rich clusters (Coma and A1367), several groups, and many filamentary structures belonging to the "Great Wall", at the approximate distance of 100 Mpc. At this distance the galaxy census is complete to Mi=-17.5 mag, i.e. approx 4 mag fainter than M*. The morphological classification of galaxies into early- (ellipt…
Using new spectroscopic observations obtained as part of the VIMOS Ultra-Deep Survey (VUDS), we perform a systematic search for overdense environments in the early universe ($z>2$) and report here on the discovery of Cl J0227-0421, a massive protocluster at $z=3.29$. This protocluster is characterized by both the large overdensity of spectroscopically confirmed members, $δ_{gal}=10.5\pm2.8$, and a significant overdensity in photometric redshift members. The halo mass of this protocluster is estimated, by a variety of methods, to be roughly $3\times10^{14}$ $\mathcal{M}_{\odot}$ at $z\sim3.3$, …
